Calculate excess weight from current weight and height, or estimate % excess weight loss from starting weight, current weight and ideal BMI.
- All Health and Medical Calculators
- All Weight Calculators
- Ideal Weight Calculator
- Ideal Waist Size Calculator
Excess Weight Formula
The calculator uses a different formula for each mode.
Excess weight from height (Quick mode):
Excess weight = Current weight − (Target BMI × Height²)
Percent excess weight loss (%EWL mode):
%EWL = (Starting weight − Current weight) / (Starting weight − Ideal weight) × 100
Excess weight from a known ideal:
Excess weight = Actual weight − Ideal weight
- Current / Actual weight — what you weigh now.
- Starting weight — your weight at the start of tracking, often the pre-op weight in bariatric care.
- Ideal weight — the reference weight, either entered directly or computed from a target BMI.
- Target BMI — the BMI value used to define ideal weight (BMI 25 is the standard upper bound of the adult healthy range).
- Height — measured in meters when applied in the BMI formula.
Heights and weights are converted to metric internally (kg and m). BMI-based ideal weight is a screening estimate for adults; it does not adjust for muscle mass, frame size, age, or pregnancy. For pediatric or clinical decisions, use a method appropriate to the patient.
Reference Tables
Use these to interpret the numbers the calculator returns.
| BMI | Adult category |
|---|---|
| Below 18.5 | Underweight |
| 18.5 – 24.9 | Healthy range |
| 25.0 – 29.9 | Overweight |
| 30.0 – 34.9 | Obesity class I |
| 35.0 – 39.9 | Obesity class II |
| 40.0 and above | Obesity class III |
%EWL benchmarks commonly used after bariatric surgery:
| %EWL | Typical interpretation |
|---|---|
| Below 25% | Insufficient weight loss |
| 25% – 49% | Suboptimal, in progress |
| 50% – 74% | Successful outcome |
| 75% and above | Excellent outcome |
Worked Example
A person is 5 ft 8 in (1.727 m) and weighs 230 lb (104.3 kg). Using a BMI 25 target:
- Ideal weight = 25 × 1.727² = 74.6 kg (about 164 lb)
- Excess weight = 104.3 − 74.6 = 29.7 kg (about 66 lb)
After surgery they drop to 180 lb (81.6 kg). %EWL:
- Weight lost = 230 − 180 = 50 lb
- Starting excess = 230 − 164 = 66 lb
- %EWL = 50 / 66 × 100 = 75.8%
FAQ
Which target BMI should you use? BMI 25 is the standard cutoff between healthy weight and overweight, and it is the most common reference for ideal weight in clinical and bariatric settings. Lower targets (22 or 23) are sometimes used for athletic or research contexts.
Why does my %EWL change if I switch the target BMI? %EWL depends on ideal weight, and ideal weight depends on the target BMI you choose. A lower target BMI raises starting excess, which lowers the %EWL value for the same amount of weight lost.
Can %EWL go above 100%? Yes. If your current weight is below the ideal weight defined by your target BMI, %EWL exceeds 100%.
Is excess weight the same as body fat? No. Excess weight is the gap between current and ideal weight on the scale. It does not measure fat mass directly and does not separate fat from muscle.
